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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 10 January 2013 by Kevin C

Update 21/02/2013: Troy Masters is doing some interestinganalysis on the methods employed here and by Foster and Rahmstorf. On the basis of his results and my latest analysis I now think that the uncertainties presented here are significantly underestimated, and that the attribution of short term temperature trends is far from settled. There remains a lot of interesting work to be done on this subject.

As a simple illustration of where the myth goes wrong, the following video clarifies how the interplay of natural and human factors have affected the short-term temperature trends, and demonstrates that underneath the short-term noise, the long-term human-caused global warming trend remains as strong as ever.

In particular, once the short-term warming and cooling influences of volcanic eruptions, solar activity, and El Niño and La Niña events are statistically removed from the temperature record, there is no evidence of a change in the rate of greenhouse warming. This replicates the result of a study by Foster and Rahmstorf (2011) under slightly different assumptions.

The human contribution to global warming over the last 16 years is essentially the same as during the prior 16 years¹. Human-caused greenhouse warming, while partially hidden by natural variations, has continued in line with model projections². Unless greenhouse gas emissions are brought under control, we will see faster warming in the future³.

Further Reading:

The results of this analysis are consistent with a statement by WMO Secretary-General Michel Jarraud:

"Naturally occurring climate variability due to phenomena such as El Niño and La Niña impact on temperatures and precipitation on a seasonal to annual scale. But they do not alter the underlying long-term trend of rising temperatures due to climate change as a result of human activities"

Footnotes:We have attempted to keep the language in this video at the same non-technical level as the media stories it refutes. As a result, it has been necessary to simplify much of the terminology. The following notes are for technically literate readers.¹ i.e. If a change in gradient is allowed at 1997 then the change in gradient is not statistically significant (even at the 1σ level).² i.e. Within the envelope of AR4 trend projections.³ On the basis of both AR4 projections and that global GHG emissions are increasing.

Update 21/02/2013: Troy Masters is doing some interestinganalysis on the methods employed here and by Foster and Rahmstorf. On the basis of his results and my latest analysis I now think that the uncertainties presented here are significantly underestimated, and that the attribution of short term temperature trends is far from settled. There remains a lot of interesting work to be done on this subject.

Superb. That the "skeptics" and those in denial have to keep pushing this particular meme speaks to their desperation. The sad part is that unless the media and public are educated/informed about such nuanced issues the "skeptics" will be able to keep trying to push this meme.

Even as we speak Monckton and his enablers are scheming as how to cherry pick those time windows of time that produce statistically insignificant temperature trends. Unbelievable but true.

So, hopefully this video can be used by the media to educate and inform the public. That way, people will turn a blind eye to ridiculous "skeptic" antics and efforts to obfuscate and the informed public will also be in a position to expose the disingenuous games of fake skeptics whenever they try and push it again.

Few presentations cut through the obfustication, contradictions and worse that constitute denier talking points as succinctly and clearly as this. Well done Kevin C; and well done also to Daniel Bailey for his excellent voice over. The sheer quality of this presentation will spark, I have no doubt, another round of conspiracy theories as the deniers refuse to admit that this work was done entirely by volunteers determined to cut through their bullshit to allow people to see the truth of global warming.

By the way, there's a myth pervading the media that this year's Met Office global surface temperature prediction shows that global warming has 'stalled'. We'll have a post with a specific rebuttal to those articles tomorrow, which makes use of Kevin's video.

Kevin C - Thanks for this excellent teaching tool. One could speak a thousand words about the cooling effect of volcanic aerosols and the cyclical nature of ENSO being superimposed on AGW and it wouldn't sink in nearly as deeply as watching this 2-minute video. Nice work!

Alexandre @11's comment caused me to go look at all the SkS climate graphics, and it is quite an impressive collection. Don't forget to add this one!

Animating the removal of forcings such as ENSO, solar and volcanic, is a brilliant way to get the message across. I will be keeping this post in mind, as I attempt to debunk contrarian nonsense in other venues.

Thanks for the effort, Kevin and Daniel. I hope it gets translated, the same way the Debunking Handbook has been.

Thanks for the accolades and plaudits, everyone, but Kevin C is the real star here. Kevin did all the heavy lifting: concepting, storyboarding, scripting, programming and editing. Others contributed, but this is his moment.

Not sure where to put this thought, but the left sidebar has a "Most used" climate myths list. What about having a "Trending" or "Currently hot" climate myths list for claims that are currently getting some media attention?

I'll my voice to congratulate you on a brilliant piece of work. The animation is excellent. It's interesting that the recent 16 year "trend", once removed the ENSO/volcanic influences, is actually a smidge faster than the trend since 1980...

Philippe: Thanks. But don't over-interpret the slight change in trend, it is not remotely statistically significant - it's noise. Depending on the assumptions you make the difference can go either way - I just showed the most parsimonious model using all the data.

Indeed using a 2-box model on the whole 130 years and taking into account the CFC reductions after Copenhagen the temperature trend is projected to be very marginally less after the mid 90's. Copenhagen really made a difference.

Really nice animation and description. These kinds of videos have real communication power to reach large audiences that may have neitehr the time nor the inclination to read the literature. Well done!

Leo Hickman's article is pretty poor IMHO - far too much time devoted to known denial enablers, such as Tisdale or the Daily Fail. Throughout the piece, Hickman demonstrates precious little comprehension of the concept that the change in trend is statistically insignificant, while the long-term trend remains strongly statistically significant. The long-term trend is, in many cases, steeper when you include post-2000 data than it is when you leave it out. Does that sound like a "slowing down"? Remedial stats class required! Armed with this information, Hickman could actually critically evaluate whether the likes of Tisdale or the Mail had anything worthwhile to say, rather than uncritically repeating the nonsense. Leo, if you read this, please do some proper critical analysis before repeating everything you read on the Internet!

A ray in the confusion of the article is the posting of this great video, however.

I assume that the corrections for natural causes depend on indexes? Which indexes have been used and why that index? I have faith that the indexes and values are (largely) correct, but I'm just asking to have answers before the other side of the mirror does...

The "pauses" and "no warming for * years" brigade from been in full cry recently, no doubt hoping to disract from the extreme weather news from around the globe (UK 2nd wettest year ever, Sandy largest exra-tropical cyclone, USA warmest year ever, Australian heat records shattered, Arctic lowest ever ice extent, extreme cold records broken in China and Russia).

The use of GISTEMP was on the basis of coverage - see this figure:Figure 1: Coverage maps for various temperature series. Colors represent mean change in temperature between the periods 1996-2000 and 2006-2010, from +2C (dark red) to -2C (dark blue). Note that the cylindrical projection exaggerates the polar regions of the map.

The other indices don't have good coverage at the poles where, according to GISTEMP, UAH and the NCEP/NCAR reanalysis dataset warming has been fastest over the 15 year period shown.

If my analysis of HadCRUT4 here is correct, then this is particularly serious over the period post 1998, with coverage bias in HadCRUT4 shifting from a warm bias around 1998 to a cool bias now. Of course UAH is the only set of measurements we have for these regions, and probably suffers ground contamination over the antarctic, however the possibility that there is a huge cooling trend over one of the poles which hasn't been picked up by any observations or models is farfetched.

On this basis I think that GISTEMP is the best choice for measuring global trends. I'm working on kriging HadCRUT4 to provide a global version for comparison.

Thanks for the explanation. I have been spending some time over at denialist sites (while they let me) and they are heavily pushing the line 'that there has been no statistically significant warming for the last 16 year meme.' Of course, they are being deceitful as there has been no statistically cooling (or statistically significant anything for that matter) over the same period. They didn't like to be reminded that the hottest 12 years in the last 34 have been in the last 11 years, and adding that people in Australia were sweltering under very hot conditions, so much so that the Australian Bureau of Meteorology (BOM) had to EXTEND the colour pattern used in their temperature maps by two additional colour to represent temperatures between 50 and 54 degrees Celsius (before the extension the hottest shade (black) went to 50 degrees).

Peeve @41, the BOM extended the graph to encompass predictions in days 6 and 7 of a 7 day forecast; ie, the period of minimum skill. Since then the forecast temperatures for those two days (Sunday 13th and Monday 14th) have declined significantly so that the peak predicted temperatures are now between 46 and 48 degrees C.

As it happens, over the last few days a total of seven minimum temperature records for individual stations have been set in India. That means currently the world ratio of maximum temperature records to minimum temperature records is 2.71, the third lowest in the last 13 years (including 2013), and well below the average of the last twelve years of 10.39. It is, of course, early days yet.

Kevin C, thanks, but I wasn't entirely clear. I actually meant the solar, volcanic and ENSO forcings... I think I recognized the use of the Multivariate ENSO Index (MEI) from NOAA (ESRL), but how about the others?

Oh, I see. MEI, PMOD, and the file tau_line.txt from the GISS modelforce site.
There does seem to be some debate as to the scaling of the volcanic term to make a forcing - GISS and Isaac Held use the same sort of value (~-20), but the Potsdam value is rather smaller. I adopted the GISS scaling, because it gave the most conservative (lowest trend) result and because gives the best fit in the 2-box model. I'd like to look into the literature on this, but have not had time.

Allow me to pile on with the compliments -- this is an incredibly effective and extremely well-presented video. Congratulations on an outstanding job.

I have a question as well -- has there been any attempt to include in the model the role of increased emission of sulfate aerosols due to the huge increase in coal burning plants in China and the rest of the world? Anything in the published literature? Satellite measurements of increased solar relection for example? Thanks.

JoeT: Good question. The only way I've tested that is in a more recent calculation where I allow the trend post 1997 to be different to the trend pre 1997. You do get a very small difference, but it's less than 1 σ and so indistinguishable from noise.

I'm not very well read on aerosol measurements, but I think Kaufmann worked his out on the basis of fuel usage. The issues is complicated by the fact that aerosols are not well mixed through the atmosphere and have different effects depending on where they are.

BTW if you look at my post 29 in the thread "IPCC Temperature Projections Have Been Exceptionally Accurate" there is a plot of the averaged ten data sets in our SKS trend feature, but now temp anomaly plotted against log base two (conc/conc 1850). I think present thread is an appropriate place to mention that plot. Dead fit to straight line with probability no correlation abscissa and ordinate less than one in 10,000.

Gents, I this is truly an excellent presentation. It's a shame the comments have been disabled on YouTube. Your were certainly engaging most of the big pseudo-skeptics in that milieu. The comments policy was helpful in maintaining reasonably civil discussion. However, I would imagine the number of comments were a bit much to moderate.

But once again from someone who visits the site constantly thank you all. It is most helpful.

Rugbyguy... We certainly appreciated your contributions on the Youtube channel comments. We discussed internally how to manage the comments on the channel and, basically, Youtube's system is just not set up for moderation as it's done here at SkS. John would have to give out his password to multiple people and every moderation action would be done as if John were doing it, regardless of who actually did it. It would be a huge land mine of potential conflicts. And on top of that, it just doubles the work of moderation when we have two discussion threads; one here and one on Youtube.

Ultimately, we decided, any video we post will also have a blog post here connected to it. All the people on Youtube (skeptics included) are welcome to post their thoughts and observations here.

Chris Mooney has this recent article out discussing how the tone of a comments section can act to polarize people when commenting goes negative. Youtube is rife with hyper-negative comments threads, especially on the climate issue. We would like to avoid driving people apart. We would prefer that people come here where we can administer our policies of keeping the discussion on topic and about the science, without personal attacks.

My sense is that most of the guys who were commenting on YT will not come here and participate. SkS has proven over and over again that skeptics can participate in discussions, but this is a more challenging atmosphere due to the fact that there are well informed people here and the commenting policies are strictly enforced. Those who are just looking for a fight will do well to keep their commenting limited to YT channels. Those who want to participate in substantive discussions should be more than willing to participate here.

At first I also thought disabling comments was a poor choice (I can already hear the cries of "SkS silences discussion!"), but when I saw that there was a prominently-displayed link to the comments section here, I changed my mind. In my experiences, talking about climate on YouTube is a nightmare. The character limits mean you end up posting as many as a dozen replies to explain a single idea, and the reply system, while better than it once was, still makes it difficult to follow the conversation.

Registering an account here is quick and simple, so that's not a sufficient excuse for anyone who wants to also claim any sort of interest in the discussion. The strategy, while also likely simplifying moderation, might also work to draw in more people like me, who don't have a great degree of knowledge or formal training on climate science. That would be a great thing because SkS, while becoming more and more widely read, still seems to mostly attract commenters who are either quite familiar with the subject or are so invested in their pseudo-scientific ideas (and sometimes conspiracy theories) that they aren't likely to learn much. Maybe a YouTube presence can change the audience for the better.